1. Field of the Invention
This invention relates to a connected structure, more particularly, to a connected structure including a supporting member and a bushing mounting member connected thereto for use as, for example, an automobile suspension arm or an engine mount.
2. Description of the Related Art
FIG. 8A shows a conventional automobile suspension arm 50 used as an upper arm, a lower arm, a trailing arm or a torsion arm. The suspension arm 50 includes a rod-shape supporting portion 51 and a bushing mounting portion 52 formed at opposite ends of the supporting portion 51. The bushing mounting portion 52 may be formed at one end of the supporting portion 51. The bushing mounting portion 52 has a circular opening 53 for mounting a columnar vibroisolating bushing 60. The bushing 60 includes, for example, a central supporting member 61, an outer rigid sleeve 62 having an outer diameter slightly larger than the inner diameter of the opening 53, and a rubber elastic member 63 disposed between the center supporting member 61 and the outer rigid sleeve 62. The bushing 60 is press-fitted in the opening 53. As shown in FIG. 8A, the supporting portion 51 is provided with a plurality of penetrated holes 54.
The above suspension arm 50 has been manufactured by cutting an extruded article having a cross-section corresponding to the cross-section of the suspension arm 50 to have a predetermined thickness in the direction of the extrusion.
Therefore, the supporting portion 51 is formed to have a rectangular shape in cross-section as shown in FIG. 8B. Such a rectangular cross-sectional shape of the supporting portion 51 inherently deteriorates the efficiency for utilizing the surrounding space. Further, the supporting portion 51 makes the whole suspension arm 50 heavy because the supporting portion 51 is formed to be non-hollow article.
It may be possible to manufacture the suspension arm 50 by separately preparing the supporting portion 51 and the bushing mounting portion 52, and then integrally joining them by a melt welding such as a MIG welding (metal electrode inert gas welding) and a TIG welding (tungsten-inert-gas arc welding), However, since the heat quantity of the melt welding is large, the rubber elastic member 63 of the bushing 60, which is press-fitted in the bushing mounting body 52, is influenced by the heat generated during the welding to cause the change of its characteristic. Further, such a large heat quantity may cause a poor joint between the supporting body 51 and the bushing mounting body 52, and/or a thermal fatigue of the supporting body 51 and the bushing mounting body 52.